Pacemaker which reestablishes or keeps the physiological electric conduction of the heart and a method of application

ABSTRACT

A pacemaker is disclosed which reestablishes or keeps the physiological electric conduction of the heart and a method of application. The pacemaker is a pulse generator, it has a ventricular output including at least two superimposed monopolar pulsewaves of reversed polarity between each other, with programmable configuration, with respect to a neutral which can be the pacemaker&#39;s metallic box or a third electrode in the case of a tripolar catheter. The catheter can have a deflectable sheath, with an electrode on its distal tip. The invention consists of a new pacemaker, and a method of application in the right ventricular septum, being able to use in order to facilitate the implantation and to avoid the connection and the disconnection, a sheath to check a proper place and then screw the catheter in said place. This method and the pacemaker are the responsible of reestablishing or preserving the physiological electrical conduction of the heart due to the creation of an alternative electric circuit and to the creation of a virtual electrode.

I. BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a new pacemaker which reestablishes or keeps the physiological electric synchrony of the heart and a method of application in the right ventricular septum, being possible to use, in order to facilitate the implantation and to avoid the connection and disconnection, a sheath to check a proper place and then screw the catheter in said place.

This method together with the pacemaker are responsible for the reestablishment and preservation of the physiological electric synchrony of the heart and is herein referred to as “EB (Electric Bypass)” due to the obtention of an alternative electric circuit and to the creation of the virtual electrode.

With the pacemaker of my invention and its method of application, a septal ventricular stimulation system with a high performance electrical and contractile synchrony is produced, thus significantly changing the implantation of a definitive pacemaker, making them more physiological. In the examples where my invention was applied, several patients with QRS narrowing were tested as well as those suffering disorders in the AV atrio-ventricular and intraventricular impulse conduction. The results show the QRS narrowing phenomena and the orientation of the depolarization with similar vectors compared to those of a depolarization by the His-Purkinje system.

2. Description of the Prior Art

A pacemaker is an electronic apparatus that produces electric impulses, intended to stimulate the cardiac muscle. The number of impulses produced per minute is called frequency. The mechanism is fed from electric power from batteries. These electric impulses are conducted to the heart by means of a cable (or electrode), so that the pacemaker itself (or pulse generator) is placed at a quite shallow surface underneath the skin, while the electrode is placed much more deeply inside the organism, up to the heart.

The first pacemakers, asynchronous, were only blind instruments that continuously produced 70 electric impulses per minute, carrying them up to the heart by means of an electrode. The electronic circuit consisted of a few diodes, transistors, resistors and a capacitor. One or more batteries provided the necessary power to feed the circuit and stimulate the heart. These pacemakers complied very well with their role when the patient's own rhythm was absolutely absent. However when the failure in the rhythm was just intermittent, the pacemaker slightly interfered with the normal rhythm, at the moments when it was reestablished.

Afterwards, the more intelligent pacemakers came out, Pacemakers on demand, that stopped functioning when the cardiac rhythm was reestablished. This supposed the introduction of new circuits, capable of detecting the electronic activity of the heart and new pacemakers were called “on demand” since they just started working when they were necessary.

Pacemakers on demand may be implanted in the atrium, in order to treat failures in the sinus node; or in the ventricle so as to treat the heart block.

An important advance in the development of programmable pacemakers was to make them more versatile. The first ones only worked under a frequency set in factory, with fixed pulse energy and were able to detect certain level of cardiac electric activity also fixed.

It may be interesting to be able to change the stimulation frequency at certain moments, adjusting it to the organic needs. In other cases, a decrease in the pulse energy may be advantageous to save power and extend the duration of the pacemaker, or on the contrary, increase it if the muscle became resistant. In some patients, it would be useful to get the pacemaker to have higher or lower capacity for detecting electric impulses, in order to eliminate the influence of abnormal rhythms, or external interferences. All of the above-mentioned options became possible with the introduction of the Programmable Pacemaker.

Currently, different kinds of these pacemakers are available, which allow the adjustment of their function to different states of healthy or sick organism without causing any discomfort to the patient.

Programmable pacemakers are insensitive to the needs of the organism and their functioning is to be changed from the outside, so that their adaptability is relative. There are other kinds of pacemakers which are more physiological, that is to say, more capable of meeting the organic needs at every moment, with its continues fluctuation. In cases where the formation of the cardiac stimulus in the atria is maintained, and the problem lies on the conduction block between the atria and the ventricles, a kind of pacemaker which senses atrial activity and then stimulates the ventricles can be introduced. These are the “atrial triggered” pacemakers, which constitute a practical reality, once the problems of implanting two catheters, one in the auricle and the other in the ventricle, are solved. In these pacemakers, as the variations in the atrial rhythm depend on organic needs variations, the pacemaker is led by the body needs

Currently, for cases where it is not possible to use atrial guidance, pacemakers have been developed that are capable of sensing other parameters in the body activity, changing automatically their frequency (self-programming frequency pacemakers). Some pacemakers catch vibrations of the body during movement; others detect breathing activity and accelerate frequency of the heart in combination with the frequency of breathing; others detect fine vibrations in the cardiac electric activity caused by exercise and others being at the stage of design or project respond to the exhaustion of oxygen in blood, to changes in body temperature, or even to many of these causes.

First pacemakers were big and short-lasting. They weighted one hundred grams, had a diameter of 7-8 cm, and 2-3 cm of thickness, wrapped with silicone rubber toughly applied. They were fed by mercury-zinc batteries that could last no more than 2-3 years. Electrodes broke frequently because of the phenomenon called “fatigue of materials”.

Nowadays, size has been reduced by a quarter or a fifth, weight has been reduced to less than a third, duration reaches 5-10 years according to the designs, and electrodes are made of a certain design and material that practically prevent their breaking and allow energy savings.

At present, we have smaller pacemakers, more powerful, long lasting, more versatile and more comfortable for the patient.

Traditional ventricular stimulation in the apex of the right ventricle (RV) is well known in the art, which through several years of use, it has shown an important reliance as regards permanence of the catheter in the correct place, control of the cardiac frequency and facility for its implantation. FIG. 9 illustrates a chart that shows right ventricular stimulation, “Standard Bipolar Stimulation on apex of RV”. However, day after day it is proven that regardless of the fact that it keeps atrio-ventricular synchrony through stimulation of both chambers, results are far away from causing a real physiological synchrony. Right ventricular stimulation on the apex of RV generates a pattern of electric activation, asynchronous in itself and therefore asynchronous left ventricular contraction.

On the other hand, stimulation in the apex of the RV can lead to non-homogenous left ventricular contraction, myofibril erradication, and disorders of myocardic perfussion. This generates an increase in the morbidity and mortality of these patients, therefore leading from several years ago to look for other places of unique and simultaneous stimulation in order to improve electric and hemodynamic parameters of permanent stimulation.

As it can be seen novelty in pacemakers was only slightly related to the place of application of electrodes. In the new pacemaker of my invention, it can be seen as an advantage, apart from those described in the previous art, when applied on patients with pacemaker indication with preserved interventricular contraction, it prevents from deleterious effects of the traditional pacemaker over the ventricular function.

Also there are some advantages for patients with disorders in intraventricular impulse conduction and allows the re-establishment of the normal intraventricular activation sequency.

Other advantage is that in patients who suffered from heart failure with blockage in its left branch, allows me to apply well-known advantages of re-synchronization through using only one catheter, so as to obtain the electric alternative circuit procedure that we herewith call EB Electric Bypass.

As already known, traditional ventricular stimulation in the apex of right ventricle (RV) has shown along the years, great trust as regards its permanence, control of the cardiac frequency and ease for its introduction. However, day by day it has been proved that regardless the fact that it keeps atrio-ventricular synchrony through stimulation of both chambers, results are far away of causing a real phyisological synchrony. Right ventricular stimulation on apex of RV generates a pattern of electric activity, asynchronic in itself and therefore contraction and asynchronic left ventricular contraction.

On the other hand, stimulation in the apex of the RV can lead to non-homogenous left ventricular contraction, myofibril erradication, and disorders of myocardic perfussion. These disorders cause an increase in the morbidity and mortality of these patients, therefore leading from several years ago to look for other places of unique and simultaneous stimulation in order to improve electric and hemodynamic parameters of constant stimulation.

In the illustrative examples attached to the present invention its significant usefulness is shown, in presence of left ventricular dysfunction with dual-chamber (AV) pacing, resynchronizing its activity with only one catheter in RV septum, without the need of special electrophysiologist training, as seen in FIG. 9. Therefore the potential outbreak in the use of the pacemaker of my invention for constant stimulation is shown.

II. SUMMARY OF THE INVENTION

According to a preferred embodiment of the present invention, a pacemaker is disclosed which reestablishes or keeps the physiological electric conduction of the heart and a method of application. The pacemaker is a pulse generator, it has a ventricular output including at least two superimposed monopolar pulsewaves of reversed polarity between each other, with programmable configuration, with respect to a neutral which can be the pacemaker's metallic box or a third electrode in the case of a tripolar catheter. The catheter can have a deflectable sheath, with an electrode on its distal tip. The invention consists of a new pacemaker, and a method of application in the right ventricular septum, being able to use in order to facilitate the implantation and to avoid the connection and the disconnection, a sheath to check a proper place and then screw the catheter in said place. This method and the pacemaker are the responsible of reestablishing or preserving the physiological electrical conduction of the heart due to the creation of an alternative electric circuit and to the creation of a virtual electrode.

III. BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows as an example of first case patient with an electrophysiology recording showing a narrow QRS and a septal electrical bypass stimulation according to the present invention showing just a slight widening of the QRS (first half of the figure) with a conduction sequence similar to the one of the basal QRS. FIG. 1.

FIG. 2 is an electrophysiology recording of to a patient with a complete left branch block and ventricular malfunction, the time of basal conduction from the beginning of the QRS to the deflection corresponding to the left ventricle through the distal electrode of a multipolar catheter placed in the coronary sinus (164 msec).

FIG. 3 is an electrophysiology recording showing the reduction of such time of conduction for the patient of FIG. 2 when electrical bypass stimulation according to the present invention is stimulated in septum (90 msec).

FIG. 4 is an electrophysiology recording for the patient of FIG. 2 where the electrical bypass stimulation according to the present invention is in apex of the right ventricle and keeps a conduction time to the left ventricle (169 msec) (similar to the basal time), when keeping the complete left branch block.

FIG. 5 shows an ECG of a patient with sinusal rhythm and complete block of the left branch, as the septal stimulation of high penetration electrical bypass stimulation according to the present invention “normalizes” the QRS, narrowing it. A proof of the “physiological change” in the sequence of intraventricular conduction is also the presence of the QRS narrowing, changes of the ventricular repolarization, with negative T waves in the precordial leads, probably secondary to “electrotonic memory”.

FIG. 6 is an ECG showing stimulation on apex of the right ventricle and follows a similar behavior to the presence of complete left branch block in the basal ECG and with case septal electrical bypass stimulation narrows the QRS and generates the same changes on ventricular repolarization.

FIG. 7 is an ECG showing on its left side how EB pacing captures the ventricles with narrow QRS and normal depolarization-repolarization pattern.

FIG. 8 is an ECG in a patient with left bundle branch block and where the fusion with extrasystoles coming from the right ventricle are expressed as a significantly narrow QRS.

FIG. 9 is a cross section view of the heart with the electrode in Septal EB1 stimulation.

FIG. 10 is a cross section view of the heart with the electrode in septum RV stimulation.

FIG. 11 is a cross section view of the heart with septal EB1 stimulation.

FIG. 12 is a cross section view of the heart with septal EB2 stimulation. IV.

IV. DETAILED DESCRIPTION OF THE INVENTION

This new pacemaker is intended to render a stimulation of a high septal penetration as already mentioned called herein “EB (Electric Bypass)” as previously mentioned, and which consists of a real approach to the permanent physiological pacing.

Apart from the method for application to facilitate the implantation and to avoid the connection and disconnection of the catheter, a deflectable sheath can be used with an electrode on its edge which allows a stimulation to verify the proper place and then screw the catheter in said place. This sheath is removed after finding the proper place for stimulation and is eventually disposable.

Likewise, in the present invention apart from the new pacemaker and its method of application, a new right septal stimulation is described, which allows the generation of a wave front with simultaneous ventricular depolarization and QRS narrowing either in patients with normal QRS or in those with conduction disorders.

The normal conduction throughout the His-Purkinje system produces a fast synchronic sequential depolarization of the myocardial fibers causing a more efficient ventricular contraction. It is already known that the best place for pacing to prevent the ventricular dissynchrony keeping its normal activity while applying the catheter is the His bundle.

Several methods have been developed to reach the His Bundle by septal stimulation. However there were several troubles in its implementation, requiring special treatment for finding the catheter, with variable results.

Together with the pacing system including the new pacemaker and its method of application, by septal implementation the wavefront penetration to the Hisian mainstream is obtained. The result is a narrow QRS, similar to the one in the normal conduction and with an almost normal hemodynamic efficiency.

With reference to FIGS. 11 and 12, a heart H is shown in cross-section showing a right ventricle RV and a left ventricle LV divided by a septum S. A catheter is provided in the right ventricle RV with a distal electrode 12 secured to the septum and a proximal electrode 14 in the right ventricle. The right-hand side of the figures show the catheter 10 enlarged and energized by a pacemaker 1 to create two monopolar pulsewaves between the electrodes 12, 14 and the pacemaker 1. FIGS. 11 and 12 differ only in the figures show two different phases for the pulsewaves.

The present pacemaker 1 is a pulse generator, single-chambered or dual-chambered, with conventional features: it has a ventricular output including at least two superimposed monopolar pulsewaves of reversed polarity between each other, with programmable configuration, in respect to a neutral which can be the pacemaker's metallic box or a third electrode in the case of a tripolar catheter. The distal electrode 12 of this catheter 10 is fixed in the right ventricular RV septum S for the ventricular stimulation, thus producing an electrical alternative circuit or Electrical Bypass (EB) of the bundle block, being a non-conventional cardiac stimulation application place, so we are in the presence of a new use by the creation of a virtual electrode for the physiological electric synchrony of the heart. Two charts showing two different options can be seen in FIGS. 9 and 10. One of them is entitled “Septal Stimulation EB1” and the other is entitled “Septal Stimulation EB2”. In FIG. 9 (Septal Stimulation EB1), the distal electrode 14 is secured to the apex of the right ventricle RV. In FIG. 10, the distal electrode is secured to the septum S.

In each of FIGS. 9 and 10, the heart H is shown divided into regions 1-5. In FIG. 9, Region 1 is the left ventricle postero basal side. Region 2 is the left ventricle lateral. Region 3 is the right ventricle basal side. Region 4 is the apex right ventricle septum apical and Region 5 is the apex left ventricle. In FIG. 10, Region 1 is the left ventricle postero basal side. Region 2 is the left ventricle lateral. Region 3 is the apex left ventricle. Region 4 is the apex right ventricle septum apical and Region 5 is the right ventricle lateral.

In the method of application and the way to facilitate the implantation and to avoid the connection and disconnection of the catheter, a deflectable sheath with an electrode in its edge can be used, which allows stimulation, in order to check the proper place and then screw the catheter in said place. This sheath is removed after finding the proper stimulation place and is eventually disposable.

This new pacemaker and its method of application consist of:

-   -   A pulse generator, single-chambered or dual-chambered, with         conventional features: it has a ventricular output including at         least two superimposed monopolar pulsewaves of reversed polarity         between each other, with programmable configuration, in respect         to a neutral which can be the pacemaker's metallic box or a         third electrode in the case of a tripolar catheter.     -   A conventional active-fixation ventricular catheter.     -   A deflectable sheath with an electrode on its distal tip.     -   The stimulation place in the right interventricular septum.     -   The right interventricular septum stimulation place, is the one         which allows a greater interventricular synchrony making the         left stimulation easier and the application of the electric         alternative circuit principle or Electrical Bypass that         reestablishes the physiological conduction of the heart when         damaged.

Apart from the new pacemaker and its method of application with the deflectable sheath with an electrode on its edge, the present invention describes a new technique for the right septal stimulation which allows the generation of a wave front with simultaneous ventricular depolarization and QRS narrowing either in patients with normal QRS or in those with conduction disorders.

This is obtained by the formation of a virtual electrode which generates a stimulation field significantly higher than the one in a traditional electrode for the physiological stimulation. Said higher current field allows to compromise more distant areas than the pacemaker place even overcoming conduction disorders, —electrical bypass (EB)—. The use of said virtual electrode assures an energy saving with regards to the necessary high output and makes the placing in the septum easier avoiding difficult electrophysiological mapping procedures.

For a better comprehension of the present invention, a septal ventricular stimulation system with high performance in the electric and probably contractile synchrony, is described. This system is intended to significantly modify the definitive pacemaker implantation, making it more physiological. Patients with QRS narrowing were tested, as well as patients with AV atrio-ventricular and interventricular conduction disturbances, showing in all of them the QRS narrowing phenomena and the orientation of the depolarization with vectors similar to those in the depolarization through the His-Purkinje system.

EXAMPLES

The embodiments of my invention are shown in the application of traditional pacemakers made in 50 consecutive patients who were stimulated in right septum with standard bipolar catheters. They were used for the record of the His bundle activity and with the pacing technique of my invention, pacemakers, method of application and a special high penetration technique of system EB.

In order to use a conventional voltage a pulse generator driven by a traditional over-stimulation pacemaker was used, with programming outputs from 1 to 36 volts and two types of waves, a sequential biphasic and another superimposed biphasic wave, with pulse widths programmable from 0.1 to 2 milliseconds. The second wave uses each electrode individually with reference to an indifferent one with opposed polarities. This allows the use of a traditional output and generating a virtual electrode of great magnitude of current which is the objective of EB stimulation (Electrical Bypass), and reducing the use of high energy with the results previously tested.

In order to know the behavior of the left ventricle in normal patients and with several branch conduction disturbances, a multipolar catheter through the coronary sinus was used. The distal dipole represents the side basal portions of the left ventricle, as it was recently shown by CARTO® search.

Forty-nine patients were successively analyzed at the EP Lab during the procedures to evaluate sinus function and A-V conduction.

These patients were divided in two groups:

Group A (31 patients) was tested with pacing on edge of RV and in septum with high output (20 volt).

Group B (18 patients) was tested with the pacing stimulation of my invention, with the EB alternative electric pathway in septum.

In both groups the duration of the QRS was measured, both the basal as well as during the different types of stimulation. In order to test the activation in basal and distal portions of the left ventricle, the gap between the beginning of the QRS and the depolarization in the coronary sinus of the most distant portion of the left ventricle was measured.

Table 1 describes the results in relation to features and magnitude of the width of the QWRS obtained in each case.

SVD- QRS BASAL sSEP sAPEX R-VI EB-VI VI EST 1 BCR1 160 100 — — — — EB 2 BCR1 220 140 — — — — EB 3 BCR1 215 154 214 154 90 169 EB 4 BCR1 140 90 120 80 70 90 EB 5 BCR1 180 128 — 120 76 — EB 6 ANG 92 104 144 — — — EB 7 ANG 120 150 240 — — — EB 8 ANG 84 96 140 40 64 112 EB 9 ANG 80 88 120 36 42 86 EB 10 ANG 72 88 120 40 68 92 EB 11 ANG 78 82 144 58 58 100 EB 12 BCRD 150 150 — — — — EB 13 HBAI 90 100 150 — — — EB BCRD+ 14 HBAI 146 120 165 — — — EB 15 BCRD 120 110 150 — — — EB 16 ANG 60 70 — — — — EB BCRD+ 17 HBAI 120 130 190 — — — EB BCRD+ 18 HBAI 140 100 — 68 70 98 EB 19 ANG 70 85 — — — — 20 mA 20 ANG 80 100 — — — — 20 mA 21 HBAI 100 110 180 — — — 20 mA BCRD+ 22 HBAI 160 120 190 — — — 20 mA 23 ANG 90 100 — — — — 20 mA 24 ANG 70 85 — — — — 20 mA 25 ANG 80 100 180 — — — 20 mA 26 ANG 80 100 — — — — 20 mA 27 ANG 70 100 — — — — 20 mA 28 ANG 65 90 — — — — 20 mA 29 BCRD 110 140 — — — — 20 mA 30 ANG 60 70 — — — — 20 mA 31 ANG 60 65 — — — — 20 mA 32 ANG 80 90 — — — — 20 mA 33 ANG 80 90 — — — — 20 mA 34 ANG 50 80 110 — — — 20 mA 35 ANG 60 76 — — — — 20 mA 36 HBAI 100 170 — — — — 20 mA BCRD+ 37 HABI 120 125 170 — — — 20 mA 38 HBAI 80 100 170 — — — 20 mA 39 HBAI 50 100 160 — — — 20 mA 40 BCRD 64 70 — — — — 20 mA 41 ANG 55 130 160 — — — 20 mA 42 ANG 60 70 — — — — 20 mA 43 ANG 90 100 140 — — — 20 mA 44 BCRI 100 120 180 — — — 20 mA 45 ANG 70 110 — — — — 20 mA 46 ANG 80 95 — — — — 20 mA BCRD+ 47 HABI 120 130 180 — — — 20 mA 48 ANG 85 140 — — — — 20 mA 49 ANG 70 85 — — — — 20 mA 50 ANG 120 140 180 — — — 20 mA

References: measures are expressed in milliseconds; narrow ANG=QRS lower than 100 msec; sSEP=width of QRS in septal stimulation; sAPEX=width of QRS with stimulation from apex of RV; R-LF=conduction time from R to a record of RV from the coronary cavity; EB-RV=conduction time from septal stimulation EB to a record of RV from the coronary cavity; sRV-LV=conduction time from stimulation on apex of RV to a record of the LV from coronary cavity; EST=features of stimulation; 20 mA=traditional stimulation with output of 20 mAmperes.

As described in the table above, there are no major differences between QRS EB and the spontaneous QRS. The average, QRS EB has 14 msec more than the spontaneous QRS. This delay is caused by a delta wave at the beginning of the QRS due to the septal penetration through a muscular pathway before the arrival of the stimulus to the specialized conduction system. Then the remaining depolarization is exactly the same as the normal QRS configuration. Differences regarding septal stimulation were not observed either when it was performed with higher energy (20 volts).

In the cases where RV apex was paced, a marked difference in spike-to-LV interval versus spike-to-LV(EB)interval was observed, LV activity being recorded as previously explained from the distal dipole of a multipolar catheter located in the coronary sinus. In average, the conduction time from the apex of RV to LV is increased by 54 msec in respect to the septal stimulation time EB to LV. This significant shortage of left-ventricle to right-ventricle time is also registered because of the presence of complete left branch block in the basal ECG, wherein the QRS significantly narrows (39 msec average) after EB stimulation. It is also accompanied by significant narrowing of the QRS in both cases (61 msec average), which supposes a more effective electric re-synchronization of the left ventricle.

FIG. 1 shows as an example of case 1, a patient with narrow QRS. Septal EB stimulation shows just a slight widening of the QRS (first half of the figure) with a conduction sequence similar to the one of the basal QRS. FIG. 1. FIG. 2 corresponds to a patient with a complete left branch block and ventricular malfunction, the time of basal conduction from the beginning of the QRS to the deflection corresponding to the left ventricle through the distal electrode of a multipolar catheter placed in the coronary sinus (164 msec). FIG. 3 shows the reduction of such time of conduction when EB is stimulated in septum (90 msec). FIG. 3.

FIG. 4 shows the same patient, the stimulation in apex of the right ventricle keeps a conduction time to the left ventricle (169 msec (similar to the basal time), when keeping the complete left branch block. FIG. 5 shows a ECG of a patient with sinusal rhythm and complete block of the left branch, as the septal stimulation of high penetration (EB) “normalizes” the QRS, narrowing it. A proof of the “physiological” change in the sequence of intraventricular conduction is also the presence of the QRS narrowing, changes of the ventricular repolarization, with negative T waves in the precordial leads, certainly secondary to “electrotonic memory”. Stimulation on apex of the right ventricle follows a behavior similar to the presence of the complete left branch block in the basal ECG. In this case septal EB stimulation narrows the QRS and generates the same changes of the ventricular repolarization (FIG. 6).

In three cases, stimulation was conducted after the radiofrequency AV node ablation, in order to avoid the high frequency response in cases of paroxystic atrial fibrillation. In these patients septal stimulation showed ventricular capture, from the same place wherein ablation was realized, with narrow QRS despite of the proper complete AV block obtained.

FIG. 7 shows the bypass of the ablation site and the narrow capture of the QRS. On the right of the record the basal rhythm is VVI pacemaker mode with complete AV block post ablation of the AV node. Note the presence of the atria dissociated from the ventricles in the “ablat” channel. At the left side, stimulation EB, from the ablation catheter in the same place of the ablation captures the ventricles with narrow QRS and normal depolarization-repolarization.

Septal EB stimulation shows a significant narrowing of the QRS similar to the normal conduction, through the His Purkinje system. It is possible to interpret this fact as an entrance of the wavefront to the His bundle, due to the special features of the EB stimulation. In some cases, the QRS similarity so suggests. However, in some circumstances, particularly when the previous QRS has a delay by the presence of the branch block, a significant narrowing is observed, similar to the one observed in the simultaneous stimulation of both ventricles (re-synchronization).

FIG. 8. In a patient with left bundle branch block, the fusion with extrasystoles coming from the right ventricle are expressed as a significantly narrow QRS. 

1. A method comprising: delivering electrostimulation pulses to a first septal location in the right ventricle of the heart near a His bundle to stimulate the conduction system of the heart near the His bundle, the electrostimulation pulses comprising at least partially overlapping opposite polarity signals; determining if a resulting contraction of the ventricles elicited via the delivery of the electrostimulation pulses to the first location exhibits one or more of a normal depolarization-repolarization pattern and a narrow QRS; delivering the electrostimulation pulses to a second septal location in response to a determination that the resulting contraction of the ventricles elicited via the delivery of the electrostimulation pulses to the first location did not exhibit one or more of a normal depolarization-repolarization pattern and a narrow QRS width; and securing an electrode at the second septal location in response to a determination that the contraction elicited in response to delivering electrostimulation pulses to the second septal location exhibits one or more of a normal depolarization-repolarization pattern and a narrow QRS width.
 2. The method of claim 1, wherein determining if a resulting contraction of the ventricles exhibits one or more of a normal depolarization-repolarization pattern and a narrow QRS includes determining if the depolarization-repolarization pattern of the resulting contraction includes a delay shorter than a delay associated with a conduction abnormality, the delays determined from an earliest QRS activation to the deflection corresponding to the left ventricle activation measured by a catheter placed in the coronary sinus.
 3. The method of claim 1, wherein determining if a resulting contraction of the ventricles exhibits one or more of a normal depolarization-repolarization pattern and a narrow QRS includes determining whether the QRS width of the resulting contraction is narrower than a QRS width associated with a conduction abnormality.
 4. The method of claim 1, wherein the heart manifests a bundle branch block that results in a QRS width that is longer in duration than a corresponding QRS width in the absence of the bundle branch block.
 5. The method of claim 1, wherein the heart manifests a left bundle branch block that results in a QRS width that is longer in duration than a corresponding QRS width in the absence of the left bundle branch block.
 6. The method of claim 1, wherein the heart manifests a bundle branch block that results in a large intrinsic QRS width and wherein the resulting contraction exhibits a narrow QRS relative to the intrinsic QRS width.
 7. The method of claim 1, wherein the location in the right ventricle of the heart is sufficiently near a blocked region of the His bundle to produce electrical bypass of the blocked region.
 8. The method of claim 1, wherein the delivered electrostimulation pulses improve the synchronicity of ventricular contractions in the heart, the improvement relative to intrinsic ventricular contractions.
 9. The method of claim 1, comprising: using a sheath including at least one sheath electrode to deliver the electrostimulation pulses at the septal location in the right ventricle of the heart near the His bundle.
 10. The method of claim 9, comprising: using the sheath to guide a catheter to a septal location at which contraction elicited via the electrostimulation pulses exhibits one or more of a normal depolarization-repolarization pattern and a narrow QRS width as compared with an QRS width associated with a conduction abnormality.
 11. The method of claim 10, comprising: receiving a signal indicative of electrical conduction of the heart in response to the delivered electrostimulation pulses; in response to the received signal indicative of electrical conduction of the heart, providing a feedback signal useful for indicating that the at least one sheath electrode is at a location which is sufficiently near the His bundle to provide electrical bypass of a conduction abnormality of the heart.
 12. The method of claim 1, wherein delivering the electrostimulation pulses comprises delivering unipolar signals.
 13. The method of claim 1, wherein delivering the electrostimulation pulses comprises delivering biphasic electrostimulation signals.
 14. The method of claim 1, comprising, after securing the pacing electrode, removing the sheath and then delivering the electrostimulation pulses to the heart using the electrode. 